Women exposed to the HPV vaccine during pregnancy had a preterm birth rate of 7.9% compared with 7.6% for women who did not get the vaccination during pregnancy.

Inadvertent administration of the quadrivalent human papillomavirus (HPV) vaccine during periconception or pregnancy does not confer additional risk to mothers and their infants, reports Obstetrics & Gynecology.1

Earlier studies of inadvertent HPV vaccine administration did not find any unusual increases in adverse maternal or fetal outcomes when comparing women who were vaccinated in periconception or pregnancy vs women who had not received the vaccine during those times.2-5

Heather S. Lipkind, MD, MS, from Yale University School of Medicine, New Haven, Connecticut, and colleagues sought to assess the safety of the quadrivalent HPV vaccine administered inadvertently during periconception or during pregnancy.

The retrospective, observational cohort study compared data from 7 sites of the Vaccine Safety Datalink of insured women 13 to 27 years of age who had singleton pregnancies between January 1, 2007, and September 1, 2013, and had received the quadrivalent HPV vaccine 2 weeks before to 2 weeks after their last menstrual period (n=720), during pregnancy (n=638), or during both periods with women who gave birth during the same time and had received the quadrivalent HPV vaccine 4 to 18 months before their last menstrual period (n=8196).

Women exposed to the vaccine during pregnancy had a preterm birth rate of 7.9% compared with 7.6% for women who were not vaccinated during pregnancy (adjusted relative risk [RR] 0.97; 95% CI, 0.72-1.3). Major birth defects occurred infants born to 2.0% of women vaccinated during pregnancy vs 1.8% of infants born to women not exposed to the vaccine (adjusted prevalence ratio 1.0; 95% CI, 0.52-1.9).

Women who were inadvertently vaccinated during periconception had a preterm birth rate of 7.4% vs 7.6% for women who did not undergo vaccination during periconception (RR 0.92; 95% CI, 0.69-1.22). Major birth defects occurred at the same rate of 1.8% in infants of women in both groups (adjusted prevalence ratio 1.04; 95% CI, 0.75-1.5).

Of the 147 nonmanufacturer reports to the Vaccine Adverse Event Reporting System about pregnant women who received the HPV vaccine from June 2006 to December 2013, none were for unexpected maternal or fetal events. The 2 major birth defects reported during this time were lower limb and cardiac defects. The most common adverse events were spontaneous abortion, elective termination of pregnancy, and maternal fever.

“Although we are reassured by the safety on maternal and infant outcomes associated with the inadvertent receipt of HPV vaccination in pregnancy, we are not advocating for routine HPV vaccination during the periconceptional period or during pregnancy and would still ask about pregnancy risks prior to giving the vaccination in the office setting,” cautions Dr Lipkind in an email interview with Infectious Disease Advisor. “We would delay the HPV vaccination to the postpartum period if pregnancy has occurred.”

Limitations

The study excluded women and girls who did not have continuous health insurance, which may have biased the results.

Vaccines administered 6 months before the participants' last period might not have been included in the data set.

Though the researchers compared overall trends of births defects with study participants and the Vaccine Safety Datalink population, they had limited access to information on the birth defects.

Disclosures

Allison L. Naleway, PhD, has received research support from Merck, Medimmune, and Pfizer. Nicola P. Klein, MD, PhD, has received research support from GlaxoSmithKline, Sanofi Pasteur, Merck & Co., Pfizer, Medimmune, Novartis (now GlaxoSmithKline), and Protein Science. Rulin C. Hechter, MD, PhD, has received research support from GlaxoSmithKline. Michael L. Jackson, PhD, MPH, has received research support from Sanofi Pasteur.